1. Field of the Invention
The present invention relates to a liquid-jet recording head for recording on recording media by discharging liquid-drops from nozzles.
2. Description of the Related Art
In ink-jet printers that record images on recording media by discharging ink-drops, in order to achieve both high-quality printing and high-speed printing, it is useful to use a recording head with nozzles having different discharging amounts.
FIG. 7A is a perspective view of a recording head having such nozzles. This recording head 1000 is mounted on a so-called serial printer. The serial printer prints desired images by repeating recording on recording media row-by-row while conveying the recording media in the column direction. Therefore, this recording head 1000 is movable in the direction perpendicular to the direction of conveyance of the recording media (not shown). A discharging surface 903 with a plurality of nozzle columns is provided in the recording head 1000 so as to face the recording media. The nozzle columns are disposed perpendicular to the moving direction of the recording head. Each nozzle column consists of, for example, large nozzles 101a discharging ink-drops of 3 to 7 pl (picoliter) and small nozzles 101b discharging ink-drops of 1 to 2 pl (picoliter), disposed alternately and substantially parallel to the direction of conveyance of the recording media. In the case of printing at a high resolution, the small nozzles 101b discharging the smaller ink-drops are used. In the case of printing at a low resolution, the large nozzles 101a discharging the larger ink-drops are used. As examples of such a recording head, PCT Japanese Translation patent Publication No. 2003-508257 and Japanese Patent Laid-Open No. 5-201003 are given.
In the above known recording head, the smaller the volume of the smaller ink-drops, the higher the resolution of the recording. At the same time, the number of drops required for a certain print density increases because the recorded area per drop decreases. Therefore, in order to maintain a constant printing speed by discharging the smaller ink-drops, it is required to discharge them at higher frequency than the larger ink-drops.
Some of the known recording heads have increased discharging frequency of the smaller ink-drops as compared with discharging the larger ink-drops. However, there remains a huge gap between the printing speed for high-quality recording by using mainly the smaller ink-drops and that for high-speed recording by using mainly the larger ink-drops.